Driving while intoxicated by marijuana is a serious concern. Almost half of 12th graders have tried marijuana and 1 in 4 have driven under its influence.1 Currently there is no brief standardized assessment that can be administered and analyzed with minimal training to test for impairment from marijuana intoxication. This study will evaluate the sensitivity of two tasks that can be administered with minimal training and time in comparison with an abbreviated simulated drive on the dose-dependent effects of marijuana (placebo, 200 mcg/kg and 300 mcg/kg). Fifty healthy, occasional users of marijuana will be recruited to participate in three visits each during which they will complete the Lane Change Test, The Attention Assessment and a simulated drive at multiple time intervals. It is hypothesized that all tasks will show a dose dependent impairment in performance immediately following marijuana use and that impairment will diminish over time. It is further hypothesized that the Lane Change Test and The Attention Assessment, which provide quick and easy summary statistics of impairment, will be suitable for use in workplace assessment of marijuana intoxication. PUBLIC HEALTH RELEVANCE: Driving while intoxicated by marijuana is a serious public health concern as almost half of 12th graders have tried marijuana and 1 in 4 have driven under its influence. This study will evaluate the sensitivity of the Lane Change Task and The Attention Assessment in comparison with simulated driving on the ability to detect marijuana impairment at multiple time points and doses. Identification of fast, reliable, assessments that can be conducted with minimal training will aid in the detection of driving impairment due to marijuana and potentially decrease its prevalence, thereby saving lives.